Seasonal variations of the Antarctic coastal ocean in the vicinity of Lützow‐Holm Bay

Abstract

During the period of 1990–1992, year‐round oceanographic observations were conducted in the vicinity of Lützow‐Holm Bay, East Antarctica. It was found that the thickness of the Winter Water (WW) layer, characterized by a cold fresh oxygen‐rich water, exhibits its maximum in the austral fall (typically 500 m) and its minimum in the austral summer (typically 350–400 m). The associated density variation of the water column explains only about one third of the seasonal variations in sea level at the coast, which suggests a large seasonal variation in barotropic coastal flow. Prominent freshening occurs in the WW layer during fall. This appears to be caused by the accumulation of WW, whose upper portion is freshened in the preceding summer. These seasonal variations appear to occur every year. We propose that the seasonal variation in the WW layer is mainly caused by the seasonal variation in the wind over the coastal ocean. In fall the prevailing easterly wind intensifies, which increases the Ekman convergence of WW in the coastal ocean, while in summer the opposite occurs.

Post-fledging and winter migration of Adélie penguins Pygoscelis adeliae in the Mawson region of East Antarctica

“…From there, in the second half of winter, the adults turned northward and one returned toward the east at latitudes of 61 to 63°S. The westward journey of post-moult adults took place at speeds similar to the westward current in that region (Tchernia & Jeannin 1984, Allison 1989, Ohshima et al 1996, Heil & Allison 1999. The eastward return of the pen-guin carrying PTT 2670 occurred sufficiently far north for the bird to take advantage of currents flowing in the other direction (Orsi et al 1995, Emery et al 1997, Heil & Allison 1999 while remaining within the packice (Figs.…”

“…Average travel speeds of the fledglings during March and April (Table 2) tended to be greater than measured ice-drift speeds (Tchernia & Jeannin 1984, Ohshima et al 1996, Heil & Allison 1999, indicating that the PTTs remained attached to the penguins over this period, at least. From May onward travel speeds and directions were more typical of expected ice movements and thus we were less confident in assuming that the instruments were still on the birds.…”

Eddy-resolving simulations of the Fimbul Ice Shelf cavity circulation: Basal melting and exchange with open ocean

“…This buoyant water mass forms within a thin layer at the ocean surface during the sea ice melt season. The subduction of ASW near the ice front is a typical feature observed along the Eastern Weddell Sea coast (Ohshima et al, 1996;Årthun et al, 2012;Graham et al, 2013). Our work explores the role of ASW and upper ocean processes in basal melting, which has received little attention in the literature to date.…”

The cyclonic circulation in the Australian–Antarctic basin simulated by an eddy-resolving general circulation model

“…Historically, iceberg drift trajectories have been used to examine the surface current on the slope and its variation (e.g., Gordon and Tchernia 1972;Tchernia and Jeannin 1980;Ohshima et al 1996;Gladstone et al 2001). However, quantitative estimates were difficult due to the uneven sampling of the data.…”